Agate Fossil Beds National Monument

Agate Fossil Beds National Monument



Birds are the most visible type of wildlife at Agate. At least 73 bird species have been identified in the park, including some year round residents such as the ring neck pheasant and the sharp-tailed grouse, and others such as the orchard oriole or wood duck are only present during the summer. Migratory birds that rest here on their way to other destinations include Canada geese and Sandhill cranes.
Agate’s bird diversity is in part due to the Niobrara River, which creates an extensive wetland and riparian area in the park. This area is moister and cooler than the upland areas and attracts birds such as the red winged blackbird, who are easily identified by their jet black bodies and red or yellow wing patches. Marsh wrens, killdeer, belted kingfisher, blue heron, and Northern rough-winged swallows also frequent the wetland areas, making this the most diverse bird area on the park. Blue herons are a large, graceful crane-like bird, whose back and wings are a blue-gray giving the heron its name. They stand up to 52” tall and wade in the river and ponds in search of fish.
The grassy upland prairie area is above the wetlands, below the rocky buttes along the park trails and roads. The grasses provide cover for the birds and their nests, which are often built on the ground. In this area visitors commonly sight lark sparrows, western meadowlarks, ring neck pheasant, horned larks and grasshopper sparrows. Meadowlarks are medium size, perching birds with dusty brown wings and a bright yellow chest.
The third distinct bird habitat type is the rocky bluffs, where the ancient mammal fossils are found. Birds such as the rock wrens, lark sparrows and cliff swallows inhabit these areas. Cliff swallows build mud nests under rock outcroppings and can be identified by their dark wings and tail, rust-colored rump, chestnut throat and whitish belly. Rock wrens nest under overhanging rocks or in crevices between rocks and line their nests with feathers, wool and grasses. They are small brownish tan birds that spend most of their time in drier, rocky areas.
Agate has a few birds of prey that are year round residents of the park and a few that are seasonally present. The red tailed hawks are year round residents with a nest near the Niobrara, but search the entire western end of the park for food. Great horned owls nest year round in trees at the west end of the park, but are seen throughout the park during the night while they search for rodents. Summer residents include golden eagles, barn owls, prairie falcons and Swainson’s hawks. Winter residents are rough-legged hawk, short-eared owls and occasionally bald eagles.


Agate’s rich prairie environment provides year round homes for many species of mammals and seasonal hunting grounds for others. With over 30 species of mammals, visitors are sure to glimpse some of the more common ones such as the white tail and mule deer browsing on grasses and shrubs within the park. Small brownish gray cottontail rabbits thrive on the moist grass around the Visitor Center and Museum, while sandy colored jackrabbits blend in well with grass along the trails. Some of the others are more elusive and nocturnal.
Predators are animals that actively hunt for smaller animals. The predators at Agate include coyotes, swift foxes, red foxes, long tailed weasels, mink and badgers. Most predators are nocturnal, meaning they are active by night and are usually seen at dusk or early morning. Most predators hunt for rodents and other small mammals, insects, amphibians and birds.
Coyotes, red foxes and swift foxes belong to the family Canidae, which also includes domestic dogs and wolves. Coyotes prey upon small rodents, rabbits, and young or sick deer, sometimes hunting in small groups of two or three. It is not uncommon to sight one at dusk or very early in the morning crossing the prairie. Coyotes are dusty gray to light brown, weigh 20 to 50 pounds, run with their tails down and look very similar to a medium sized dog. The foxes are distinguished from coyotes by their smaller size, weighing 15 to 20 pounds, and their bushy tail. Red foxes tend to be red brown to a dull black with white in the tip of the tail and black paws while swift foxes have a pale buffy-yellow coat with black spots on either side of their snout and tip of tail. Red foxes maintain a mixed diet of small birds, rabbits, rodents, insects, berries and nuts. Swift foxes prefer a diet of small mammals but do feed on insects. Swift foxes are only rarely sighted in the park but are known to be in this area.
Minks, badgers and the long-tailed weasel belong to the family Mustelidae. They are characterized by a nocturnal, solitary lifestyle of eating small rodents, rabbits and aquatic life. Badgers are the largest of this family found in the area, weighing up to 25 pounds. The powerful burrowers hunt rodents and rabbits by using their large claws to dig up dens. Badgers are identified by a shaggy gray to brown coat, short bushy tail, white stripe on their face and dark colored feet. With thick fur, a loose tough hide, and heavy neck muscles to protect it as it bites, claws, and exudes (not spraying) a skunk-like musk, badgers are a formidable fighter. The smallest predator of the area is the long-tailed weasel that hunts small rodents up to the size of a jack rabbit. The long tail weasel’s body and head is 8” - 10” long, it has 4” - 6” tail, and it weighs around seven ounces. The home range of this weasel is about 30 - 40 acres and populations are rarely larger than 15 - 20 animals per square mile. The coat of the weasel is dark brown with a black tipped tail and whitish under body. Though rarely seen, weasels make their home at Agate Fossil Beds, nesting in abandoned burrows of other animals. Minks are larger than the weasel, weighing one to three pounds with a body length of 12” – 17”. Minks are rich dark brown with a white chin and occasionally white spots on the belly. Minks are excellent swimmers and prefer to live along river banks hunting frogs, rodents, birds and eggs.
Several species of bats make their home in the trees and rock cliffs of the park. Species may include the silver-haired bat, red bat, hoary bat, fringed myotis, and the long legged myotis. Bats are the only flying mammal, their hands being modified into a wing that extends from the forearm to the side of the body and the hind leg. Bats use a locating system known as echolocation. The bat emits a series of super-sonic sounds that bounce off objects giving the bat their location. This allows them to fly in complete darkness and still locate prey. All bats at Agate Fossil Beds are insectivorous, meaning they eat only insects, most preferring moths and beetles.
Rodents, rabbits and other small mammals are a vital source of food for predators, which include mammals as well as birds of prey such as hawks and bald eagles. Agate’s common small rodents are the pocket gophers, kangaroo rats, pocket mice, ground squirrels, masked shrew and voles. Rodents are characterized by having two long, sharp incisors on their upper jaw and two on their lower with a significant space between incisors and grinding teeth located in the back of the jaw. At least 15 rodent species are known to be within the park, making up half of the mammal species. As there are few trees at Agate, most rodents live in the ground in burrows and feed upon insects, nuts, fruits, grasses, and occasionally meats. Some are active during the cooler hours of the day, while others prefer only to be out at night. The beaver spend their time hidden in the willows and shrubs of the riparian areas. In the winter, you may notice breathing holes in the ice on the river. This is a good indication that beaver are in the area.
Similar to the rodents are the rabbits, which also possess large incisors on the upper jaw but have smaller less obvious lower incisors. Their ears are long and they have a short cottony tail. Visitors will most likely see a desert cottontail browsing or resting near the Visitor Center and Museum. The cottontails can be distinguished from the jack rabbits by their small bodies, weighing 1 - 2¾ pounds, and fluffy white tail. Jackrabbits have long ears and larger, slimmer bodies, and are rarely sighted.
Another small mammal is the striped skunk, which is related to the weasel, mink, and badger but is considered a predator. Skunks are omnivorous, meaning they eat insects, plants and meats. They dine on insects, grubs, eggs and berries, and occasionally catch mice. Striped skunks are around the size of a house cat, black with white striped body and tail and spray a terrible odor if startled or scared. Though not related, the raccoon is similar in diet and behavior, but his body is larger, weighing 12 to 35 pounds, with a salt and pepper colored coat and a black and white ringed tail. Raccoons also have an omnivorous diet of fish, insects, berries and nuts. Both skunks and raccoons are nocturnal and solitary, spending their days in dens made of abandoned burrows, fallen trees, or rock clefts.

Hoofed grazers walk on two-part hooves formed by the third and fourth toes. The most commonly sighted of these animals are the white-tail and mule deer but pronghorns are occasionally seen, usually farther away from the Visitor Center and Museum. White-tails are easily identified by their fluffy white tails that wave while they bounce away. White-tails stand 3’ - 3½â€™ tall and weigh between 150 and 400 pounds. White-tails can run up to 40 mph and jump an impressive 30 ft. horizontally and 8½ ft. vertically. With a home range rarely over a mile wide, the white-tails at Agate spend most of their days browsing the forbs and shrubs of the wetland areas while spending hot mid-day hours resting hidden in the cattails and willows. Mule deer can be distinguished by large, mule-like ears, stockier bodies and they do not flag with their tail, meaning they do not hold it up as they run as white-tail deer usually do. Mule deer do not continually reside in the park, they wander onto neighboring fields and migrate to higher elevations during the hot summer months. Males of both species have antlers that are shed in January or February and re-grown through summer to be ready for the rut (breeding season) in November and December.

Quite different from the deer, pronghorns have evolved to live in the open environment. Their protruding eyes can see movement four miles away. They can sprint for 3 to 4 minutes at speeds up to 70 mph, settling into an easy cruise between 30 and 45 mph. Both sexes have horns, not antlers like deer, that are shed yearly and re-grown. Pronghorns cover a large territory, about two to four square miles. These animals are easily distinguished by size, standing only three feet and weighing 75 to 130 pounds, having white markings on rump, belly and throat. 

Felines are carnivorous animals with retractable claws, short faces and rounded ears. Two feline species occur in the park, mountain lions and bobcats. Mountain lions, called cougars and pumas, pass through this area in search of new territory but do not stay long as there is not enough prey or protective cover for them. Bobcats are small, stealthy creatures, usually seen at night when they are hunting small mammals and birds. Their small body (weighing 15 - 35 pounds) is tawny colored (grayer in winter), with indistinct black spotting. They have a short, stubby tail with 2 - 3 black bars and black tip above and pale or white below. Their face has thin, black lines radiating onto a broad cheek ruff with slightly tufted ears. Bobcats make their home in rock crevices, hollowed logs and under fallen trees and could possible live on or near the park. While bobcats may wander 25 - 50 miles in search of food and shelter, they generally remain within two miles of their dens.



Though rainbow trout (Oncorhynchus mykiss) were stocked in large numbers at Agate, they did not survive here. In the 1979 and 1989 surveys, none were found, sighted or reported caught. Most likely the rainbows migrated to more desirable sections of the river. During the 1989 survey, largemouth bass (Micropterus salmoides) and blue gill (Lepomis macrochirur) were found at the Agate Springs Ranch, which borders the park upstream. Though these two species would most likely spread to the park and could already be present, neither is native to the Niobrara.
The native species of the park generally do not feed on other fish as the non-natives do. They feed mostly on insects and algae, are smaller in size than the non-native species, and tolerate a wide range of temperatures. Northern pike pose a threat to native populations due to their excessive predatation, which native fish are not adapted to survive. There are several additional species of minnows that were probably native to the Niobrara but are currently absent from the main stream though still found in small tributaries. It is possible that these do not occur due to predatation from trout or pike in the river channel.
The non-native brown trout was once abundant at Agate but has seen a population decrease in recent times. They are large, hardy fish that can reach over 30 pounds. They feed on invertebrates (mostly insects) and smaller fish. Brown trout are identified by prominent spots on their back and sides, often red or orange and accented with halos and a tail fin generally free of spots. Introduced from Europe in 1883, browns make their home in cold water streams across the northeast and western United States. Though it is not a native, it is a naturalized species - meaning it has adapted to the stream and reproduces unlike the rainbow. The decrease of the brown trout population could be the result of several factors, but is directly connected with the lack of stocking since 1997.
A voracious newcomer to the park is the northern pike, which was probably introduced from Box Butte Reservoir, 38 miles downstream of Agate, as a result of the 1991 flood of the Upper Niobrara drainage system. Northern pike consume three to four times their weight in a year. They prey mostly on fish, including other pikes, but will consume frogs, small mammals, birds, and anything else they can catch. Their slim, trim cylindrical bodies and deeply forked tails are designed for quick speed, and their elongated snout and sharp teeth are used to capture prey efficiently. The color pattern of the northern pike is distinguished by a pattern of horizontal rows of yellow to white bean shaped spots with an olive green to brown background. In some regions, the pike is prized by fisherman for its size, which can easily be over 10 pounds and up to 50, but at Agate there have not been any large specimens reported.
During the fish surveys of 1979 and 1989, the most commonly found fish at Agate was the creek chub. Chubs are widely distributed throughout the Great Plains, inhabiting rocky and sandy pools of headwaters, creeks and small rivers. They can tolerate temperature fluctuations from 0º - 31º C ( 32º - 49 º F) and can survive in isolated pools, but need flowing water to reproduce. Adult creek chubs can be identified by their size, usually 5” – 8” inches but up to 12” in length, a dark blotch at the front of the dorsal (back) fin base and near the tail, and a large mouth with an upper jaw reaching beyond the eye.



There are at least 16 species of reptiles identified at Agate Fossil Beds National Monument. The abundance of food and cover makes excellent habitat for snakes, turtles and one species of lizard. Reptiles are cold blooded animals, meaning they regulate their temperature from outside sources. Mammals are warm blooded and energy is used to keep the body at a specific temperature. Reptiles bask, or rest in the sun, to warm themselves and burrow into the ground, or hide under rocks or in water to cool themselves.
There is a wide variety of snakes at Agate, including at least 12 documented species. Most commonly sighted are the bullsnake, prairie rattler, hognose and garter snake. Snakes are distinguished by their elongated body, lack of appendages (arms and legs), and they have no external ear opening. All snakes at Agate are shy, and do not generally approach people or pets, preferring to hide and wait for danger to pass. Rattlesnakes rattle their tail as a warning that they are there and do not want to be disturbed. If a visitor does encounter a rattlesnake, or a snake they cannot identify, wait for it to pass, or slowly walk away from it and let a ranger know. To protect the rattlesnakes and visitors, park staff move them away from the trails and Visitor Center to less traveled areas of the park.
One species of lizard is known to be present at Agate, the short-horned lizard, sometimes called the horny toad. This little guy is commonly sited around the rocks near the Fossil Hills trail. Short-horned lizards are between two and six inches long with pointy spines on their head and body. They are most active in the heat of the day and burrow into the soil at night to stay warm. They feed mostly on ants but occasionally eat other insects.
From the big snapping turtles to the colorful painted turtle, turtles are fun to see and watch. There are three species of turtles documented at Agate, snapping, painted and spiny soft-shell, which is not commonly seen. Visitors who patiently watch might see a snapping turtle that weighs up to 45 pounds with a shell measuring 18 inches long. Even the smaller snappers are easily identified by their hooked jaws, massive heads, long tails and darkly colored shells. Snappers feed on invertebrates, aquatic plants, carrion, birds, small mammals and fish. Though they are excellent swimmers and spend most of their time in the water or buried in mud, they can travel overland several miles at a time. The painted turtles are smaller, ranging from 4”-10” and are identified by their colors. Their shell is olive to black with the segments of the shell lined with red; neck, legs and tail are striped with red and yellow. Painted turtles spend most of their time in the water, or very close to it, and enjoy basking on partially submerged logs and debris. Young painteds have a carnivorous diet, meaning they eat mostly meat, but grow to prefer a herbaceous diet of aquatic plants and reeds after a few years.


The prairie might not seem like the best climate for amphibians, but Agate boasts at least six species: three frogs, two toads and one salamander. The most commonly sighted amphibian at the park is probably the Woodhouse's toad, or the western chorus frog.

The Niobrara River banks create a wetland and riparian area that is a haven for amphibians, who need moisture to survive and reproduce. Amphibians are animals that have two life stages, a larval, aquatic form and an adult, terrestrial form. Tadpoles are the larval stage of frogs and toads and live in water until developing legs and lungs. Salamanders have a similar larval stage, and then develop lungs and can live outside of water but still require moisture.

The barred tiger salamander is the largest land-dwelling salamander in the United States, ranging in length from 6" to 13". These animals burrow in damp meadows and in abandoned burrows of small mammals. They mate in backwater pools and lay egg masses on submerged debris. Woodhouse's toads are found in areas of irrigation, such as around the Visitor's Center and Museum and in riparian areas. The toads prefer sandy soils to burrow in and spend most of the day hiding, coming out at night to catch flies. The chorus frog is greenish brown and active mostly at night, but can be spotted in the early morning in grassy areas that are dry or swampy.

Insects, Spiders, Centipedes, Millipedes

Insects and spiders are the most abundant animal at Agate Fossil Beds, as they are across the world. Summer visitors can hardly miss seeing at least one or two species of insects and evidence of more. Though insects are not most people's favorite animals, they are an important part of the ecosystem. Some pollinate flowers, prey on pest species, and fertilize and aerate the soil.  Other insects break down deceased animals.

Insects and spiders are similar and both belong to the Phylum Anthropoda which also consists of crabs and millipedes. Within the phylum there are several classes; insects belong to the Class Insectivore, spiders belong to the Class Arachnid. Insects and spiders are both invertebrates, meaning they have no backbone. Instead, they have an exoskeleton. The exoskeleton is the hard outside of the animal that can be shed when the insect grows and then be re-grown (a process known as molting). Insects include butterflies, beetles, bugs, and flies. All of which have six legs, three body sections and two antennae. If you look at an ant it is easy to see all these parts. Spiders differ from insects by having eight legs, no antennae and only two body sections. Spiders belong to the arachnid class which also includes ticks, mites and scorpions.

Some of the most fascinating insects at the monument are the butterflies. During a 1995 butterfly survey, 18 species of butterflies were identified, among these are the Wood Nymph, Red Admiral and California Dog Face. Butterflies are most commonly present in late spring and summer, in the riparian areas near the river, and irrigated areas near the Visitor Center and Museum. Similar to the butterfly in appearance is the moth. Both have four wings that are covered in tiny scales, develop from caterpillars and feed on flower nectar. Unlike moths, butterflies fly only during the day. Most moths have somber colors and fly at night but some have bright colors and are active by day. Butterflies hold their wings together vertically over their body while moths fold their wings over their body like a roof. One of the most notable moths at Agate is one called the miller, which develops from the army cutworm in late spring and infests houses and outbuildings before migrating. Butterflies and moths are avid pollinators of prairie plants and can commonly be seen near the river in the spring and late summer.